Enhancement: Ergonomic improvements

[AllergicMushroom]

I'd like to propose some ergonomic improvements:

1. Double click on the column creates a new card.
2. Color changing can be made from an easier place, e.g. a button next to the "+" button.
3. Implement a better color picker with more choices.

Note that I don't know if this is only related to the plugin or to Joplin itself. I'm merely opening this issue to track improvements I want and I might work on.

[laurent22]

Implement a better color picker with more choices.

The colours are selected in such a way that they work on both dark and light theme, with dark and white font color. I don't think I'd want to add more of them. Sometimes less is more

[AllergicMushroom]

I agree partially. Many people use custom CSS styles and may want other colors.